The inventors have observed that typical silicon etch processes performed on three dimensional devices, such as a fin field effect transistor (FinFET) can result in damage to the fin, for example, due to physical damage from high energy ions, chemical damage due to corrosive gases, and inadequate selectivity to silicon oxide layer that protects the fin. In addition, the inventors noted that typical silicon etch processes often change the fin shape due to micro-loading, for example, causing tapered profiles between fins and/or erosion of fins. Lastly, the inventors have observed that post etch residue can lead to loss of fins altogether and/or the formation of irregular and poor quality epitaxial layers.
Therefore, the inventors have provided improved methods for etching silicon films.